The star was chatting to director Barry Levinson in a conversation moderated by The Hollywood Reporter columnist and podcast host Scott Feinberg when talk turned to the late "Black Panther" star, who died last month aged 43 after a battle with colon cancer.
Washington, who years ago helped pay Boseman's tuition to take part in a British American Drama Academy summer programme, said, "He didn't get cheated. We did. I pray for his poor wife and his family. They got cheated, but he lived a full life."
Calling the "21 Bridges" star a "gentle soul," Washington recalled how impressed he was when he saw his younger peer take on the title role in Marvel's "Black Panther" movie.
"I went backstage and I saw Chad and I saw (director) Ryan Coogler, and then I watched the movie and I remember shedding a tear, because I thought, man, these young guys are gone. Like they'd taken over," he added.
Boseman, who was diagnosed with cancer back in 2016 but kept his illness private, paid tribute to Washington for helping him become an actor by funding his studies when the "Training Day" star was honoured with the American Film Institute's Lifetime Achievement Award 2019.